function increaseEventRange(event) { upDateEventRange(10);	}
function decreaseEventRange(event) { upDateEventRange(-10);	}

function upDateEventRange(eventIntervalChange) {			
	currentEventRangeIndex = currentEventRangeIndex + eventIntervalChange;

	if (currentEventRangeIndex <= 0) {
		currentEventRangeIndex = 1;
	}

	var upperEventIntervalBound = currentEventRangeIndex + 9;
	var eventRangeString = currentEventRangeIndex + " - " + upperEventIntervalBound;		

	document.getElementById("eventRange").innerHTML = eventRangeString;
}